• How to argue about gods


    Soon I will be writing a series of posts on the arguments of natural theology.  I’ll focus primarily (but not exclusively) on those defended by William Lane Craig, mainly because he is the most well-known Christian apologist of our day.  The arguments I have in mind are:

    1. the Kalam cosmological argument,
    2. the fine tuning argument,
    3. the moral argument,
    4. the ontological argument,
    5. the argument from the historicity of Jesus’ resurrection, and
    6. the argument from personal experience.

    I expect to cover more than just these, and I’d be happy to take requests if you’d like a particular argument covered.

    But before I get started with that, I think it would be sensible to make a few general points about philosophical argumentation in general.  Since these are important things to keep in mind when discussing all of the above arguments, it makes sense to say them once now and refer back here when needed.

    Before going further, I should mention that Graham Oppy covers a lot more ground in his excellent book, Arguing about gods, from which I have borrowed the title of this post.  As well as extensive discussions of the arguments I intend to discuss, Oppy devotes an entire chapter of nearly 50 pages to general considerations of theistic and atheistic argumentation, including the finer details of what it means to deem an argument “successful”.

    1.  Logic

    All of the arguments I consider will be in the form of logical deductions.  There will be a sequence of premises, and a conclusion.  There are two aspects to the “soundness” of an argument of this form:

    1. the conclusion must follow logically from the premises (this is to say that the argument is “valid”), and
    2. the premises must be true.

    If both these conditions are met, then any rational person is required to accept the conclusion.  If either or both of the conditions are not met, then the argument is not sound.  This is not to say that the conclusion is not true, but only that the argument does not demonstrate that the conclusion is true.  For example, consider the following argument:

    1. The sun is in the Milky Way.
    2. Anything in the Milky Way is a star.
    3. Therefore, the sun is a star.

    This argument satisfies the first condition (the argument is valid), but not the second (the second premise is false).  Therefore, the argument is not sound, even though the conclusion is true.  Here is a second example:

    1. Stars are bright.
    2. The sun is bright.
    3. Therefore, the sun is a star.

    In this case, the second condition is satisfied (both premises are true), but the first condition is not (the argument is not valid).  Even without examining the logical structure of the argument in detail, we should already be suspicious.  Indeed, if the argument was deemed sound, then we could mimic it to “prove” things that were obviously not true.  For example:

    1. Stars are bright.
    2. My torch is bright.
    3. Therefore, my torch is a star.

    But such parodies are unnecessary to defeat the original argument.  The unsound nature of the logic of both arguments may be demonstrated by noting that they take the form:

    1. Anything that has Property P also has Property Q.
    2. X has Property Q.
    3. Therefore, X has Property P.

    Here, P is the property of being a star and Q is the property of being bright.  This is an example of the logical fallacy known as affirming the consequent.  Wikipedia’s list of logical fallacies is a useful resource, but since the arguments I consider won’t have such obvious problems, I don’t need to say much more about logical fallacies.

    2.  Word play

    But there is one other kind of fallacy that can sometimes plague an argument that might otherwise appear to be valid.  Consider the following well-known example:

    1. Socrates is Greek.
    2. Greek is a language.
    3. Therefore, Socrates is a language.

    This is an example of what is known as equivocation.  Here, a word or phrase is used in two different senses to connect two otherwise disconnected ideas.  In the above example, the word that is equivocated on is “Greek”.  In the first sense, it is used to describe a person from the country Greece, and in the second it is used to describe the language such people usually speak.  Although both premises are true, the conclusion is clearly not; despite appearances (they share a common word), the premises have nothing to do with each other.

    But sometimes equivocation is more subtle than that.  Rather than a word clearly being used in two different senses, sometimes it is the scope of the word that changes.  Here is another well-known example, taken from Critical Thinking by Lavery et al:

    1. Some say it is wrong to discriminate.
    2. But people must often discriminate (choosing a marriage partner, for example).
    3. So it is not wrong to discriminate.

    Here, in both cases, discrimination means making decisions based on the qualities of the options.  But Premise 2 is speaking of discrimination based on relevant qualities, whereas Premise 1 refers to discrimination based on irrelevant qualities.  The validity of the first kind of discrimination lends no support to the validity of the second kind.

    3.  Burden of proof

    Perhaps the most important concept to grasp in relation to theistic arguments is that of the burden of proof.  Suppose Bob presents an argument like the following:

    1. If X is the case, then unicorns exist.
    2. X is the case.
    3. Therefore, unicorns exist.

    For the sake of our discussion, let’s suppose also that Premise 1 is true.  In this case, since it has a logically valid form, the argument will be successful if and only if Premise 2 is true.  So Bob must be prepared to demonstrate that X is the case.

    To make the example more concrete, suppose X refers to the existence of a unicorn skeleton.  Perhaps I am suspicious that the unicorn skeleton Bob claims to own might be a fake.  If I told Bob about this suspicion, he might ask me to prove that it is a fake, and claim that his argument will be valid unless I can succesfully do so.  But this would be to try to shift his burden of proof.  If Bob wishes to prove that a unicorn skeleton exists, it is up to him to prove that his unicorn skeleton is not a fake.  It is not up to me to prove it is a fake.  Naturally, if I could show his unicorn skeleton was a fake, then I would have undermined his argument.  But it is not necessary for me to do so.  Since Bob is making the claim, it is up to him to demonstrate it.

    Let’s consider a second example.  Suppose Sally claimed that your husband was cheating on you.  As evidence for this claim, Sally said that she saw your husband eating lunch with another woman.  You might object, and say “Maybe he was eating lunch with a work colleague”, to which Sally might respond “Can you prove she was a work colleague?”.  Of course it is not up to you to demonstrate that your husband’s lunch partner was a work colleague.  Since Sally is making the claim, she must demonstrate that your husband really is cheating on you.  And since the possibility of his lunch partner being a work colleague sheds doubt on the strength of her evidence, it is up to Sally to prove that your husband was indeed having an affair with this woman.

    Both these examples show that if you have reason to be suspicious of a premise used in an argument, it is up to the defender of the argument to show that your suspicion can be adequately dealt with.  It is not enough for them to ask you to prove that your suspected problem is an actual problem.

    For further treatment of this important topic, I highly recommend QualiaSoup’s excellent youtube video on The burden of proof.

    4.  Conclusion

    When I come to examine the theistic arguments alluded to above, it is not my goal to prove that there is no god.  In fact, I doubt that such a goal could be achieved.  Rather, my goal will be to simply prove that the theistic arguments fail for one reason or another.  To do so, I do not have to prove that any of the premises are false (although this is sometimes possible).  Rather, I have to demonstrate that one or more premises are not adequately supported.  To do this, it is usually only necessary to shed some reasonable doubt on a premise.  Often the defender of the argument will claim that this doubt is not sufficient to undermine their argument, and say that I must disprove the premise.  But this is an attempt to shift the burden of proof, and is not a valid criticism.

    Category: GodLogicPhilosophyTheismWilliam Lane Craig


    Article by: Reasonably Faithless

    Mathematician and former Christian

    One Pingback/Trackback

    • Smilodon’s Retreat

      Thanks. This is the kind of thing that I missed in college. I understand it intuitively because of my science background, but I like this.

      More in a similar vein would be appreciated.

      • Reasonably Faithless

        Thanks for the feedback, SR. I’ve got rather a lot to say about these theistic arguments….. I became a bit obsessed with them as I was leaving the Christian faith.

    • I’m looking forward to your series! With only one philosophy class under my belt, I could sorely use a refresher. — Beth 🙂

      • Reasonably Faithless

        Thanks Beth! But with one philosophy class under your belt, you have more formal qualifications than me 😛

    • bigdog

      How about this logical syllogism? Is it valid? I’m curious to know what you think.

      The only valid argument for the existence of God is a logical one.
      There are no logical arguments for the existence of God.
      Therefore God does not exist.

      • Reasonably Faithless

        Hello bigdog.

        The conclusion does not follow from the premises. The best you could conclude is “Therefore, there are no valid arguments for the existence of God”. The argument as you stated it seems to boil down to “I don’t or can’t know X is true; therefore, X is false”.

        I also think it would be very difficult to establish the two premises, even if they were true.

        The second premise supposes that one has been able to check all possible logical arguments (which seems hopelessly impossible), or has simply induced a conclusion from just noting that there don’t currently exist logical arguments for the existence of a god. In this case, who’s to say a successful one will not be discovered tomorrow?

        To establish the first, you would have to start by defining “valid argument” very precisely, especially if you want to compare logical valid arguments and non-logical valid arguments (even if this is to simply conclude that there are no such thing as the second). Are you able to do that?

        I certainly don’t claim to know the premises are true, but I suspect the second is, by virtue of thinking that it is possible that there is no God. If it is possible that X does not exist, then there can be no valid argument that X does exist. Such a means of “establishing” the premise is of course useless in the current context, since we are trying to establish it *in order to conclude* what I took as evidence that the premise itself is likely true. And I would be surprised if the first could be proved false (which doesn’t mean it is automatically true). In particular, I would be interested to know what someone might mean by a valid, but non-logical, argument. And by what means might someone show that a given non-logical argument is valid?

      • Steve Chavura

        Not valid because it introduces a fourth term: God’s existence. The proper conclusion would be: Therefore, there are no valid arguments for the existence of God.

    • Wonderfully logical! I will refer theists back here plenty of times, I think 🙂

    • DRC

      A clear and practical primer on argumentation. Looking forward to the series.

      Just wondering… Why must the burden of proof be on the one making a claim. Of course this makes sense to me intuitively, but it would be impossible for us to prove where the burden lies with any kind of logical argument, correct?

      • Reasonably Faithless

        Thanks, DRC.

        About your question, the simple answer is that it is just etiquette of philosophical discourse. But really this is the case because if it were not, then anybody could make a claim and deem it true until proved otherwise. You are welcome to believe something until proved otherwise, but you shouldn’t expect somebody else to take on your beliefs just because they can not prove you wrong. (Russell’s Teapot is the standard example.)

        About the second question, it can be tricky in a complicated discussion to determine who needs to prove what. But, for example, if Bob claims climate change is real, and wants people to believe him, he must provide evidence. If Sally claims climate change is not real, and wants people to believe her, she must provide evidence. Even if Sally simply claimed that Bob had not adequately defended his claim, it would still be up to her to demonstrate why his arguments were insufficient. The burden of proof lies with the person making the claim.

        QualiaSoup’s video on burden of proof is outstanding – I linked to it in the post above.

    • John W. Loftus

      This looks like a great series. I’m looking forward to it!

      • Thanks, John. It will be interspersed with more typical posts, as these critiques take quite a bit to produce.

    • im-skeptical

      The rules of logic are accepted by most everyone. The real trick is getting people to agree on the premises.

    • Don Sr.

      I once knew an inquisitive and sensitive young man named “J”.
      I am proud to see he has grown into a scientist of repute. A man who is leading others to the true light of understanding, and away from superstitious and prejudicial dogma.
      To quote Bertrand Russell “Persecution is used in theology, not in arithmetic, because in arithmetic there is knowledge, but in theology there is only opinion”.
      Bless you my boy!

      • Thanks, Don Sr. That means a lot. I can’t think of many Christian ministers who would say something like that!

    • Andrew


      As another Christian-turned-atheist, I wanted to ask you a question regarding burden of proof.

      I have often pointed out to theists their inherent responsibility regarding burden of proof, citing Russel’s Teapot, unicorns, etc.

      Many apologists like to dodge the burden of proof claim. They become very flippant and dismissive. There is a disconnect, I think, when it comes to theists’ perception of the worldview of atheism. In a sense, I think they like to assert that atheism is not, in fact, a default framework of beliefs and, like theism, requires its own set of proofs or demonstration.

      Here, William Lane Craig, in typical smug fashion, makes assertions to this effect: http://www.reasonablefaith.org/definition-of-atheism

      What is your response to theists who wish to dodge / dismiss the burden of proof?

      Great blog by the way, I will be back often!

      • Thanks for your kind words, Andrew. I’m glad to hear from another Christian-turned-atheist – there are many of us out there…..

        This is an interesting question, and one I will probably write a blog about. In the link you sent, Craig addressed the point quite commendably in his first paragraph.

        Suppose your Christian friend claims there is a god. If he expects you to take on this belief, it is up to him to give you reasons. If another friend claims there is no god, then she should give you reasons if she wishes you to take on this belief.

        Anyone making a claim should be prepared to back it up – or else you could claim anything, and declare yourself right unless contrary proof is given – Russell’s famous teapot is the prime example.

        But what many Christians don’t understand is that most atheists do not have a belief that there are no gods. For such a person, there is no burden of proof. To use Craig’s example, if I don’t believe there is gold on Mars, then what do I need to prove to you? But if you believe there *is* gold on Mars, then you should provide me with some evidence for this if you wish to convince me.

        It comes down to how one defines the word “atheism”. Some people use it to mean “belief that there is no god”, and others use it to mean “lack of belief in a god”. Depending on the way you use the term, there may or may not be an associated burden of proof.

        In debates, Craig often presumes his atheist opponent uses “atheist” to mean the stronger of the above definitions, and says things like “Prof X has given us no reasons to believe atheism is true”. This would be fine if Prof X has said “there is no god” but not backed up this claim. But if Prof X really has the weaker definition in mind when he calls himself an atheist, then he has no burden of proof with respect to the proposition “there is no god”. He has not claimed there is no god, and so has no need to prove it. He might be perfectly open to the possibility that there is some kind of god. This would be like a UFO believer trying to force a skeptic to prove that aliens have never visited earth, and claiming victory if they can’t prove it.

        In the end, it comes down to definitions. Some people (mostly theists) don’t like “atheist” to have the second meaning. To those people, I say:

        “Call me whatever you like. I have no belief in a god, and if that makes me an agnostic in your book, then you can think of me as an agnostic. I use the word atheist to describe my lack of belief, but it is my lack of belief that matters. I am not asserting that there is no god, so I do not have to prove that there is no god.”

        PS. If I ever did debate Craig (or a like-minded apologist), I would make quite a point of this in my opening speech.

    • Hi there,
      Just an fyi, I am writing a paper on the KCA which will eventually become a book, with any luck.

      I have posted a couple of pieces on it recently:




      let me know what you think! If you want to chat about the kca, mail me!

      • Great, thanks JP. I’ve seen your first post, and am starting to have a bit more time to read stuff, so will check out the rest shortly. I’m looking forward to your book. Have you read Graham Oppy’s “Philosophical perspectives on infinity”? He was planning to write a book on all the variations of the cosmological argument, and ended up writing a whole book about infinity!

    • Your mode of explaining all in this post is genuinely fastidious, all be able to easily know it, Thanks a lot.|

    • brad lencioni

      Great post! One small correction, though, that should be made is your use of the logical terms ‘valid’ and ‘sound’; namely, a ‘valid argument’ is one which cannot have both false premises and a true conclusion (which can be demonstrated by a truth table)–full stop; and a ‘sound argument’ is one that is both valid and consists of all true premises. For an argument to be valid is for its conclusion to be derived from its premises according to the rules of logic; for it to be sound (which is of ultimate value) is for it to be (1) valid, (2) contain, indeed, all true premises; and thus (3) posses a conclusion whose truth value cannot be denied.

      Peace 🙂

      • Reasonably Faithless

        Many thanks for that, Brad. You are right – I was using colloquial understandings of words that have more precise meanings in this context. I’ve updated the section accordingly. Cheers!

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